Remote controlling



Dec. 9, 1969 w. F. sAN'rELMA-NN, JR 3,483,562

lREMOTE CONTROLLING Sheets-Sheet l Filed OCC. 14, 1963 |300 CPS FIGI INVENTOR.

WILLIAM E SANTELMANN JR. BY @MMA mp ATTORNEYS Dec., 9, 1'969 w. F. SANTELMANN, JR 3,483,552

REMOTE CONTROLLING Filed not. 14,.)1953 @Sheets-Sheet 2 ma@ 00m.

United States Patent 3,483,562 REMOTE CONTRGLLING William l". Santelmann, Jr., Lexington, Mass., assignor to Automatic Radio Manufacturing Co. Inc., Boston, Mass., a corporation of Massachusetts Filed Oct. 14, 1963, Ser. No. 315,875 Int. Cl. H04b 7/ 00 US. Cl. 343-225 4 Claims ABSTRACT 0F THE DISCLOSURE A remote control system includes a low frequency receiver and a transmitter in a portable case. The transmitter includes a coil that not only helps establish the center frequency, but also establishes a near energy field for detection by the receiver. The transmitter also includes a lower frequency modulating circuit that simultaneously amplitude and frequency modulates the carrier signal. The modulating signal introduces variations in the effective capacity with a circuit including a pair of diodes forming a voltage doubler circuit having an A-C input coupled to the coil and having a D-C output coupled to a gas discharge bulb ignited in response to the occurrence of radio frequency oscillations. The bulb 23 functions as a D'C load when the voltage doubler circuit is driven at its A-C input end to help effect the desired frequency modulation without eliminating the amplitude modu lation. A fixed tuned superheterodyne receiver at the remote point responds to the near energy field and detects at least the frequency modulation to provide a control signal.

The present invention relates in general to remote controlling and more particularly concerns a novel radio control system for providing reliable on-off remote controlling at distances even beyond 50 feet while the radio receiver is relatively insensitive to false operation from noise sources, such as iiuorescent lights and universal motors employed in home appliances. The invention is especially useful in connection with garage door openers. An embodiment of the invention employs transitor circuitry throughout to enhance portability, minimize power consumption and minimize component failure. A feature of this embodiment of the invention resides in the use of relatively inexpensive standard circuit components to keep costs down while maintaining stable reliable operation without costly crystal control of frequencies with a transmitter that complies fully with FCC regulations.

The use of radio transmitters and receivers for remote control is well-known and widely used in many different fields. In particular, radio-controlled garage doors are becoming increasingly popular, not only because of the convenience involved in being able to open and close the garage door without first stopping and getting out of the car, but also from the standpoint of safety in providing no opportunity for a criminal to attack an unsuspecting driver while opening the garage door late at night.

Manufacturers of remote radio control systems for home and industrial use strive to keep these systems as low in cost as practical. To this end typical prior art systems employ a simple transmitter having a radio frequency carrier amplitude modulated with one or more audio frequency tones. The particular operating channel of a system is defined by the carrier frequency and that of the one or more tones. The complementary receiver of the system is tuned to receive the carrier frequency and respond to the one or more audio tones, demodulated from the carrier.

One typical prior art system transmits in the VHP` band without crystal control. This system is accompanied Patented Dec. 9, T969 ice by a number of disadvantages. It is difficult to maintain long term frequency stability, and the transmitter often requires retuning to achieve maximum system sensitivity. The metallic portions of an automobile have dimensions comparable to a wavelength `at these high frequencies and seriously interfere with radiation characteristics of the transmitter antenna. Since the transmitting system must not produce more than a prescribed relatively low field strength at a specified distance from the transmitter to comply with FCC regulations, transmitter detuning and reduction in antenna efhciency from design specifications seriously interferes with desirable system operation.

Another system in common use operates on the high frequency citizens band where higher radiated power levels are permitted provided that the transmitted carrier fequency is crystal controlled. While these systems are thereby free of the problem of detuning and insuicient power to operate the receiver, the increased cost of crystal control and higher power is disadvantageous. Moreover, a further and in some instances more serious disadvantage resides in the high ratio of transmitters operating in the citizens band to the narrow frequency range of that band. This crowding of the band results in increased possibility of the receiver being actuated by spurious signals.

Accordingly, it is an important object of this invention to provide a remote control system that is stable and reliable in operation, low in cost, easy to operate, yand highly insensitive to all but the desired operating signals.

It is still a further object of this invention to achieve the preceding object with a transmitter that provides both amplitude and frequency modulation in synchronism.

It is still a further object of this invention to achieve the preceding object with fully transistorized equipment that is relatively inexpensive and easy to fabricate.

It is still another object of this invention to achieve the preceding object while complying with FCC regulations.

According to the invention, means including a coil establish oscillation at a center radio frequency having a wavelength many times greater than the physical dimensions of the coil. Means frequency modulate the oscillations at the frequency that is much lower than the center radio frequency. A portable case contains the aforesaid means and supports the coil for radiating the frequency modulated oscillations at low power. Receiving means are located remote from the portable case. The receiving means includes transducing means responsive to the radiated frequency modulated oscillations for providing a corresponding frequency modulated electrical signal, amplifying means for selectively amplifying the frequency modulated signal, discriminator means for providing a signal of the mixed frequency related to the magnitude of the frequency modulation, and means for selectively amplifying the latter fixed frequency signal to provide a control signal at the location of the receiving means. The wavelength of the energy at the center radio frequency is so large that when the receiving means and the portable case are separated by a distance of 50 feet, the receiving means transducing means is in the near radiation field established by the coil.

ln a more specific form the means for establishing oscillations at the center radio frequency comprises certain elements arranged in an oscillatory circuit with the coil coacting with first capacitance means in series therewith and second capacitance means shunting the series combination of the coil and first capacitance means to determine the instantaneous radio frequency of the oscillations. The means for frequency modulating comprises a source of a signal of the said fixed frequency, typically an audio frequency, and means responsive to the fixed frequency signal for effecting variations in the effective capacity of the capacitive means to frequency modulate the said oscillations at said fixed frequency.

Numerous other features, objects and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:

FIG. 1 is a schematic circuit diagram of an exemplary embodiment of a transmitter according to the invention; and

FIG. 2 is a schematic circuit diagram of an exemplary embodiment of the receiver according to the invention.

With reference now to the drawing and more particularly FIG. l thereof, there is shown a schematic circuit diagram of an exemplary embodiment of the invention. The drawing includes specific parameter values and typical observed signal waveforms at the Various points indicated. A transistor Q1 and associated circuitry cornprise a low radio frequency oscillator providing an output signal waveform 11 modulated in both frequency and amplitude by the audio signal 12 provided by transistor Q2 and associated circuitry functioning as an audio oscillator.

The radio frequency oscillator circuit includes a coil L1 -13 which functions not only to help determine the center frequency of oscillation, but also as the means for establishing an energy field at a remote receiving unit. Coil 13 is in series with first capacitive means comprising a fixed capacitor 14 and a variable capacitor 15 which coact to introduce negative reactance in series with the positive reactance furnished by coil 13 at the frequency of oscillation, typically of the order of 400 kilocycles. This series combination is shunted by second capacitive means comprising a fixed capacitor 16 and a second capacitor 17 in series, the two capacitors 16 and 17 forming a capacitive voltage divider to determine the amount of voltage developed across the tuned circuit that is fed back for application between base and emitter of transistor Q1 to sustain oscillations. The junction between coil 13 and capacitor 16 is coupled to the base of transistor Q1 by coupling capacitor 21. The effective inductive reactance shunting the capacitive reactance presented by capacitors 16 and 17 is the inductive reactance presented by coil 13 minus the capacitive reactance presented by the parallel combination of capacitors 14 and 15. This type of oscillator is especially advantageous in embodying the principles of the present invention.

The present invention adopts a mode of operation in which the wavelength of the oscillatory energy provided by transistor Q1 is much greater than the separation between transmitter and remote receiving unit during normal operation. As a result, the remote receiving unit responds primarily to the near field which the coil establishes` This near field is proportional to the product of the coil inductance and coil current. For a given current near field magnitude is increased by increasing the inductance. This choice of oscillatory circuit results in a high coil inductance for determining oscillatory radio frequency so that this same coil may also be used to establish the energy field at the remote location. This dual function of coil 13 helps to keep costs low and transmitter size compact.

The means for effecting frequency modulation comprise diodes D1 and D2, the series combination being shunted by a capacitor 22 and a neon gas discharge bulb 23 in a voltage doubler circuit with bulb 23 functioning as a D-C load when the circuit is driven at its input end with the signal at the lower end of coil 13 coupled through coupling capacitor 24. This circuit has the property that as the magnitude of the signal 11 increases, the capacitive reactance presented by the input of this voltage doubling circiut between the lower end of coil 13 and the junction between capacitors 16 and 17 decreases to decrease the instantaneous frequency of the oscillation supported and radiated by coil 13. Since the magnitude of the signal11 depends upon the degree of amplitude modulation introduced at the collector of transistor Q1 through radio frequency choke 25, the circuit arrangement results in a radiated signal having both amplitude and frequency modulation occurring at the same audio frequency in synchronism.

The source of the audio modulating signal of fixed frequency is an audio oscillator circuit of conventional design comprising a transformer 26 having a primary with an intermediate tap 27 connected to the collector of transistor Q2. Transformer 26 also has a secondary winding 31 arranged to feed back energy through capacitor 32 and parasitic suppression resistor 33. The primary of the transformer 26 is tuned by capacitor 35 to resonate substantially at the desired audio modulating frequency, typically 1300 cycles per second, the modulating signal waveform 12 appearing on the collector of transistor Q2 that is coupled by R-F choke 25 to the collector of transistor Q1.

A push button switch 37 connects the negative lead of battery 38 to the base of transistor Q1 through biasing resistor 36 and through the primary of transformer 26 to the collector of transistor Q2 to initiate the modulated oscillations.

Referring to FIG. 2, there is shown a schematic circuit diagram of a receiver in a system according to this invention. Since the configuration of many of the circuits in the receiver are well-known, the specific circuit diagram enables one skilled in the art to practice the invention. Accordingly, only a brief description of the function of most of these circuits follows so as to avoid obscuring the principles of this invention.

Transistor Q1 and associated circuitry comprise a tuned R-F amplifier stage for selectively amplifying the 400 kilocycle modulated signal radiated by the transmitter. Input transformer T1 comprises a ferri-loopstick antenna that is tuned to the center frequency. However, other antennas, such as a long wire, power lines, or telephone lines suitably coupled to the radio frequency amplifier may be used as a supplement to or substitute for the ferri-loopstick.

Transformer T2 couples the amplified radio frequency signal to the oscillator-mixer stage comprising transistor Q2' and associated circuit components to provide an output signal at the intermediate frequency, which may be 265 kilocycles, that is transmitted by transformer T3 to the I-F amplifier comprising transistor Q3 and associated circuit components. Transistor Q4, diodes D2 and D3 and associated circuit components comprise a limiter stage that is energized through transformer T5. Diodes D4 and D5 and associated circuitry coact with discriminator transformer T5 to demodulate the frequency modulated intermediate frequency signal applied to the primary of transformer T5 and produce the 1300 cycle audio signal 42 that is amplified by the amplification and impedance transforming circuits comprising transistors Q5 and Q6.

The signal from transistor Q6 is applied to the base of transistor Q7 having the tuned collector circuit comprising the primary winding of transformer T6 tuned to the 1300 cycle audio signal. Transformed T6 is a step-down transformer with a secondary that provides suicient drive to the base of transistor Q8 to render that transsistor sufiiciently conductive to produce a D-C current through relay coil 43 after rectification to close relay contacts 44 and deliver a control signal to a garage door operator or other utilization device. Diode D6 functions as a damping diode across the relay coil.

Transistor Q7 is normally nonconductive in the absence of an audio signal. While signals of different audio frequencies may render transistor Q7 conductive, only a signal corresponding to the resonant frequency of the tuned collector circuit normally develops enough signal amplitude to render transistor Q8 conductive and operate the relay. This tuned collector circuit helps effect relay operation only in response to a desired operating signal.

While the specific circuit of FIG. 2 shows a separate battery for delivering energy to transistors Q7 and Q8 because it may be advantageous to supply these relatively high current stages from a lower impedance sources, these transistors may receive power from the same 9 volt source that energizes terminals 45 and 46.

ln the specific embodiment described herein, the receiver responds only to the frequency modulation on the carrier. This has been found to be adequate where excessive interference is not a problem. However, means may also be provided to detect the amplitude modulation on the intermediate frequency signal prior to the limiter stage. The detected amplitude modulated and frequency modulated signals may then be applied to means, such as a synchronous detector, to provide a control signal only when energized by synchronized signals of the same fixed frequency. This technique further enhances the system control reliability.

While the signal strength radiated by the transmitter shown in FIG. 1 is low enough to meet FCC requirements, satisfactory operation is attained with a distance of 50 feet between transmitter and receiver. These results were typically obtained with coil 13 comprising 57 turns of strands No. 38 Litz wire on a 1%2 diameter form, the winding being 5/32" long and 5A6 deep. Transformer T1 was wound on a ferrite core about 3/16" in diameter encased with a shell of ferrite material whose outside diameter was about 3A and Whose height was about Ss with the annular width of the region containing the windings being about 1%6. Each of the windings was No. 34 Nyclad wire with the secondary between terminals 1 and 2 being 79 turns, the primary portion between terminals 3 and 4 being 125 turns and the primary portion between taps 4 and 5 being 441 turns.

It has been found advantageous to keep metal objects, such as the battery case, away from the coil 13 so as to minimize unwanted oscillatory loading. 1t is also preferable to house the coil 13 inside a plastic case including the transmitter, thereby keeping the effect of external capacitance, such as that introduced by a hand holding the transmitter, from appreciably affecting the transmitter frequency. The exceptionally sensitive receiver disclosed herein is preferably arranged with the ferri-loopstick antenna spaced as far as practical from audio circuits to minimize undesired electrical coupling. Transformer T6 may be electrically shield.

There has been described a novel high performance remote control system characterized by high reliability, a light-weight compact portable transmitter, and low cost. It is evident that those skilled in the art may now make numerous modifications of, departures from and uses of the specific embodiment described herein without departing from the inventive concepts. Consequently, the invention is to be construed as limited solely by the spirit and scope of the appended claims.

What is claimed is:

1. Radio controlling apparatus comprising,

means including a coil for establishing oscillations at a center radio frequency in the range of frequencies embraced by the low and medium frquency bands having a wavelength many times greater than the physical dimensions of said coil,

means for modulating said oscillations with a modulating signal having frequency much lower than said center radio frequency,

a portable case containing said aforesaid means and supporting said coil as substantially the sole means for establishing a near energy field at a point remote from said case separated from said case by a distance that is many times greater than the physical dimensions of said coil and many times less than the wavelength of said energy eld at said center frequency,

receiving means located at said remote point and including transducing means responsive to said near energy field for providing a corresponding modulated signal, amplifying means for selectively amplifying said corresponding modulated signal, means for demodulating the latter signal, and means responsive to the demodulated signal for providing a control signal,

said means including a coil comprising circuit elements arranged in an oscillatory circuit with said coil co-V acting with first capacitive means in series therewith to form a series combination shunted by second capacitive means to determine the instantaneous radio frequency of said oscillations,

said means for modulating comprising means responsive to said modulating signal for effecting variations in the effective capacity of said capacitive means to frequency modulate said oscillations,

said means responsive to said modulating signal for effecting variations in the effective capacity of said capacitive means comprising means including a pair of unilaterally conductive devices forming a voltage doubler circuit having an A-C input coupled to said coil and said capacitive means and having a D-C output,

and a gas discharge bulb coupled to said D-C output and igniting in response to the occurrence of said radio frequency oscillations.

2. Radio controlling apparatus in accordance with claim 1 wherein said means including a coil comprises a first transistor having at least base, emitter and collector electrodes,

battery means in said portable case having a potential between its terminals less than the ignition potential of said gas discharge bulb for providing operating potentials to said first transistor,

and means for selectively connecting said battery means to said first transistor to initiate said oscillations and ignite said gas discharge bulb.

3. Radio controlling apparatus comprising,

means including a coil for establishing oscillations at a center radio frequency in the range of frequencies embraced by the low and medium frequency bands having a wavelength many times greater than the physical dimensions of said coil,

means for modulating said oscillator with a modulating signal having a frequency much lower than said center radio frequency,

a'. portable case containing said aforesaid means and supporting said coil as substantially the sole means for establishing a near energy field at a point remote from said case separated from said case by a distance that is many times greater than the physical dimensions of said coil and many times less than the wavelength of said energy field at said center frequency,

and means supported by said case for selectively establishing said oscillations,

said means including a coil comprising circuit elements arranged in an oscillatory circuit with said coil coacting with first capacitive means in series therewith to form a series combination shunted by second capacitive means to determine the instantaneous radio frequency of said oscillations,

said means for modulating comprising means responsive to said modulating signal for effecting variations in the effective capacity of said capacitive means to frequency modulate said oscillations,

said means responsive to said modulating signal for effecting variations in the effective capacity of said capacitive means comprising means including a pair of unilaterally conductive devices forming a voltage doubler circuit having an A-C input coupled to said coil and said capacitive means and having a D-C output,

7 and a gas discharge bulb coupled to said DS output and igniting in response to the occurrence of said radio 'frequency oscillations. 4. Radio controlling apparatus in accordance with claim 3 wherein said means including a coil comprises a -irst transistor having at least base, emitter and collector electrodes,

battery ymeans in said portable case having a potential between its terminals less than the ignition potential of said gas discharge bulb for providing operating potentials to said rst transistor, and said means for selectively establishing said oscillalations includes means for selectively connecting said battery means to said rst transistor to initiate-'said oscillations and ignite said gas discharge bulb.

References Cited UNITED STATES PATENTS 8/1960 Parmet et al. 325-37 8 3,103,664 9/1963 Hooper 325-37 3,175,047 3/1965 Borberg 325-37 2,230,231 2/1941 Crosby 325-45 2,644,077 6/ 1953 Sharp 325-45 2,805,338 9/1957 Siebenberg 340-248 2,899,547 8/1959 Crow et al. 325-45 2,985,755 5/1961 Giesselman 343-228 3,090,959 5/1963 Marmont 343-225 3,106,711 10/196-3 Bott 343-228 3,170,113 2/1965 Harmon 325-45 3,218,610 11/1965 Brown 340-17l OTHER REFERENCES International Dictionary of Physics and Electronics, 2nd ed., Van Nostrand, 1961, p. 89.

JOHN W. CALDWELL, Primary Examiner MARSHALL M. CURTIS, Assistant Examiner U.S. Cl. X.R. 

